NEW DELHI: Shares of telecom incumbents such as Bharti Airtel, Idea Cellular and Reliance Communications nosedived up to 9 per cent on Thursday, as challenger Reliance Jio priced data tariff for its services at as low as Rs 50/GB, kicking off a tariff war.

In what could be the worst nightmare for Bharti Airtel, the current market leader, Mukesh Ambani said Reliance Jio would offer free voice services to its active users.

Shares of Bharti Airtel slumped 8.99 per cent to hit a low of Rs 302 on BSE. Shares of Idea Cellular, the third largest telecom subscriber, crashed 9.09 per cent to hit a 52-week low of Rs 85. Within 45 minutes of Mukesh Ambani Reliance AGM, Bharti lost Rs 12,000 crore in market capitalisation, while Idea Cellular eroded Rs 2,800 crore in market value.

Reliance Communications, the fourth largest operator by subscriber base, plunged 6.49 per cent to Rs 50.40.

“All voice calls for Jio customers will be absolutely free," Ambani said. Roaming charges will also be zero, Ambani said. In addition, Jio will offer data at Rs 50 per GB (base rate) against current rate of Rs 250/GB charged by peers. Jio will launch 10 plans.

"We have price points starting from Rs 19 for the occasional data user, to a monthly rate of Rs 149 plan for the light data user and all the way up to a monthly Rs 4,999 plan for the heaviest data user," Ambani said.

The venture, Reliance Jio Infocomm, will be the world's biggest startup with an investment of Rs 1,50,000 crore, the company had said in March. It is believed that the company’s subscriber base has already swelled to 25 million during trials. W

The RIL Chairman said Reliance Jio plans to cover 90 per cent of India's population by March 2017. The company will introduce 4G handsets at as low as Rs 2,999, Ambani said.

At present, Jio’s network covers 18,000 cities and two lakh villages. A set of apps that Jio offers will be free for active subscribers till December 2017, Ambani said.

“All voice calls for Jio customers will be absolutely free," Ambani said. Roaming charges will also be zero, Ambani added.

Incumbent players were tightening their belts and had announced various schemes to retain existing subscribers “We continue to remain cautious on the sector in the light of the twin risks of Jio's impending launch and the upcoming spectrum auction,” Credit Suisse said in a note.

Goldman Sachs in a note said that the response to this new entrant has been positive, with long queues in company stores. “We expect Jio to garner 35 million subscribers over the next two years, with data volume growth for incumbents slowing to 50 per cent in FY17E from 70 per cent in FY16,”it said.

The Telecom Regulatory Authority of India (Trai) pulled up Bharti Airtel and Vodafone Idea for warning subscribers of certain plans that their SIM cards would be deactivated if they do not recharge their pre-paid accounts though these subscribers had the minimum required balance.